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TPS65218D0: 5V input power circuit of PMIC

shigehiro tsuda
Mastermind 9490 points
Part Number: TPS65218D0

Hi,

Please tell me the circuit that turns off the power of the PMIC after the power down sequence is completed by turning off the 5V power supply.

Our customer thinks that it is not practical to use a large capacitor that can maintain the AM437x power down sequence completion time by shutting off the 5V power.
I think that a power supply IC is necessary before the PMIC.
Is there a suitable power supply IC?

5V power off event(mechnical switch ..etc)
PFI is detect(4.8V)
AM437x power down sequence start
AM437x power down sequence end
5V power off (IN_BIAS drops below 2.5 V)
power off(IN_BIAS is 0V)

Best Regards,
Shigehiro Tsuda

  • 0
    TI__Mastermind 30310 points

    Tsuda-san,

    PFI-->nPFO is simply a buffered comparator measuring the PFI pin vs. 0.8V with a tight tolerance.

    nPFO will go low when PFI is below the threshold. Depending on how this is wired to AM437x will determine how the circuit behaves. 

    From the PMIC side, there is an option to connect the power rails to nPFO digitally by setting the OFFnPFO bit to 1b. This I2C configuration would need to be made by the processor in advance by writing to the PMIC by I2C. If OFFnPFO bit is set, then PGOOD will go low as soon as the PMIC begins the power-down sequence.

    Other than this, the only control you have from the PMIC side is to wire-OR the nPFO pin to the PWR_EN pin (PMIC_PWR_EN signal) so that when nPFO goes low, the PMIC is also told to shut down in hardware by the PWR_EN pin as opposed to waiting for the processor to take control. 

    Let me know if this helps your understanding.

  • 0 in reply to Brian Berner
    Mastermind 9490 points

    Hi Brian,

    Thank you for quick reply and your support.

    Is there a way to send to the external device that the power-down sequence is complete?
    Does PFO apply to that?
    Please let me know if there is any good idea to control the external power IC.
    If there is a proven method, it is good.

    Best Regards,
    Shigehiro Tsuda



  • 0 in reply to shigehiro tsuda
    TI__Mastermind 30310 points

    shigehiro tsuda said:
    Is there a way to send to the external device that the power-down sequence is complete?

    In your question, what is the "external device"? Is there another IC (for example, an MCU) that would benefit from receiving a signal that power-down sequence is complete?

  • 0 in reply to Brian Berner
    Mastermind 9490 points

    Hi Brian,

    Thank you for quick reply.
    This external device is Power IC with enable function.
    This is main power supply(5V).

    Best Regards,
    Shigehiro Tsuda



     

  • 0 in reply to shigehiro tsuda
    TI__Mastermind 30310 points

    Tsuda-san,

    If I understand correctly, the main power supply will generate 5V from a higher voltage (12V, 24V, or higher) and then 5V is the input to the PMIC. Let's say it is 24V for now.

    What you are saying is that you want the Main Power Supply IC (24V-->5V) to shut down after the PMIC is done with the power-down sequence?

    Can you please draw a timing diagram of what is expected to happen?

    PFI will detect a power failure based on the resistances in the resistor divider (compared to 0.8V).

    PFI can detect a power failure of a 5V rail, but it could also detect a power-failure of an upstream rail (for example, the 24V rail).